Not sure mate, mobilemick reckons it's in the immobiliser unit, I can't confirm that as I don't know the layout of your van.
Does your van have a remote control for the radio?
If so then it is likely that the receiver in the roof is simply an infra red receiver for the radio remote.
(my 2001 espace is set up like that)
If you have an infra red plip the dome on the headlining will be the receiver
and it is worth having a look at.
Given your van is a 2002 model I would imagine it would have an RF plip like mine, not an infra red plip
, in which case it won't be the dome in the headlining
I know I said it before but I'll say it again, please be sure you have the correct resynching procedure for your vehicle as the procedure varies slightly between different models.
Sorry if I'm being patronising or something equally annoying LOL, it just seems odd that everything is working OK other than the plip not actually working the locks.
(fuses found to be OK/plip is transmitting/locking works from button on roof)
I have to agree that the receiver going bad is unlikely, please double check the resynch procedure, also: maybe mobilemick can suggest which fuse to pull for the immobiliser to attempt to reset it, just in case it comes back to that.
There are at least 2 fuses that have some relation to the immob. on my car, so figure yours will likely have more than one that you can try.
These frenchy electrics are truly a swine.
I know somewhere to check for both the procedure and the fuse locations, dunno if they have any info on your van, will have a look for you though, unfortunately I can't post a link as it may be against the forum rules.
I'll let you know whether or not I find anything.